15-Block Area Secured As Crime Scene After Boston Attack

And NPR's Tovia Smith joins us now from Boston. And, Tovia, let's recap the chronology just a little bit. Two explosions about 10 seconds apart, very close by at the finish line, correct?

TOVIA SMITH, BYLINE: That's right. About a block apart. And while, as we just heard, president was cautioning against jumping to conclusions, some White House officials are being less circumspect, calling this an act of terror. And likewise, Boston's Police commissioner, Ed Davis, suggested the same earlier today when he was asked whether this was a terrorist attack.

COMMISSIONER ED DAVIS: We're not being definitive on this right now. But you can reach the wrong conclusions based upon what happened.

SMITH: Indeed. The FBI's counterterrorism teams have been on the scene since just after these two powerful explosions that shook buildings, literally knocked some runners to the ground. It was a fiery blast, followed by a smoke, as you heard. There's been at least one more blast in the area. That was a controlled explosion of a suspicious package that was detonated on purpose by authorities.

Officials say every bag that was dropped on the street as people panicked and ran from the area is now being treated as suspicious and more controlled blasts may be ahead. The 15-block area is now secured. It's being treated as a crime scene. No word of anybody claiming responsibility. Officials say there was no threat or warning of an attack.

But authorities are looking for tips. They're at hospitals talking to the injured, looking for clues and asking anybody to call the police tip line. You can imagine how many cameras were rolling in the area all day. So they will have plenty of footage to review as well.

BLOCK: And, Tovia, the casualties are just horrific. The images that are coming out from the marathon, we mentioned two people dead, at least 93 injured by NPR's count, although other news sources have put that number quite a but higher than that.

SMITH: The numbers have been climbing up on a steep curve all afternoon and evening, no way to know if we're at the end of that. We do know the area, of course, was jam-packed with people - tourists, spectators, runners. Many, we saw from the images, were trapped under the steel barricades that were lining the route. Many were actually hit by the blast. As President Obama said, they were gravely wounded. He described it that way. They have been treated at area hospitals.

Also on the scene, it was a great help that there were so many medical tents set up for the runners right there. But, of course, those were prepared to deal with things like dehydration and certainly nothing like this, what's being described as more like battlefield injuries or something you'd see in Baghdad, not Boston.

BLOCK: Mm-hmm. And, Tovia, the Boston Marathon has always run on Patriot's Day, Massachusetts holiday. It's a time of great celebration. And to have this happen at the end of it, obviously, just a horrific, horrific end to that event, which covers a lot of ground, 26 miles from Hopkinton all the way into Boston.

SMITH: That's right. Of course, the elite runners had finished hours before this happened. We don't know who or how many may have still been in the area, but thousands were still headed there at the time. And officials are now still imploring people to stay away from the scene, trying to make sure that it's safe now.

And the mayor says he's trying to set up a new kind of alternate meeting point for runners and their friends or family who are expecting to meet up at the finish line or nearby. You can imagine there are many runners who were not carrying cell phones and probably have loved ones who would be pretty worried to say the least right now.